Computers and computing systems have impacted nearly every aspect of modern living. Computers are generally involved in work, recreation, healthcare, transportation, entertainment, household management, etc.
Mixed-reality computer systems, which include virtual-reality systems and augmented-reality systems, have recently received significant interest for their ability to create immersive experiences for users. Conventional augmented-reality systems create an augmented-reality scenario by visually presenting virtual objects in the real world. In contrast, conventional virtual-reality systems create a more immersive experience such that a user's entire view is obstructed by a virtual world. As used herein, mixed-reality, augmented-reality, and virtual-reality systems are described and referenced interchangeably. Unless specifically stated or unless specifically required, as understood by one of skill in the art, the descriptions herein apply equally to any type of mixed-reality system, including augmented-reality systems, virtual-reality systems, and/or any other similar system capable of displaying virtual objects to a user.
Mixed-reality computer systems typically use one or more on-body devices (e.g., a head-mounted device, a handheld device, etc.). The head-mounted device provides a display, sometimes referred to as a head-mounted display (hereinafter “HMD”), that enables a user to view overlapping and/or integrated visual information in the user's ambient environment. For example, a mixed-reality system may present visual information to the user, through the HMD, in the form of a simulated object on an actual table surface.
Continued advances in hardware capabilities and rendering technologies have greatly increased the realism of virtual objects and scenes displayed to a user within a mixed-reality environment. For example, in mixed-reality environments, virtual objects can be placed within the real world in such a way as to give the impression that the virtual object is part of the real world. As a user moves around within the real world, the mixed-reality environment automatically updates so that the user is provided with the proper perspective and view of the virtual object. This mixed-reality environment is often referred to as a computer-generated scene, or simply a “scene.”
In such systems, the user's body (specifically the user's head and corresponding HMD) can move in real-time in relation to the virtual environment. For example, in a mixed-reality application, if the user tilts her head in one direction, she would not expect the image or hologram to tilt with them. Ideally, the system would measure the position of the user's head and render images at a fast enough rate to eliminate any jitter or drift in the image position, as perceived by the user. However, typical graphics processing units (“GPU”) currently render frames between only 30 to 60 frames per second, depending on the quality and performance of the GPU. This results in a potential delay of 16 to 33 milliseconds between the point in time of when the head position is detected and when the image is actually displayed on the HMD. Additional latency can also be associated with the time that is required to determine the new head position and/or delays between the GPU's frame buffer and the final adjusted display. The result is a potentially large error between where the user would expect an image and where the image is actually displayed, thereby degrading the user experience. In some instances, the user can also experience discomfort and disorientation when the virtual images are not presented in the appropriate locations, particularly during movement of the user's head and HMD.
In an effort to reduce or eliminate some of the foregoing rendering errors, existing systems apply late stage corrections to make final adjustments to the image after the image rendered by the GPU. This process is performed before the pixels are displayed so as to compensate for the latest rotation, translation, and/or magnifications resulting from the user's head movement. This adjustment process is often referred to as “Late State Adjustment”, “Late Stage Reprojection”, “LSR” or “LSR Adjustments.” Hereinafter, this disclosure will use the abbreviation “LSR.” Since frames can be rendered at a high rate and with high resolution, existing systems that employ LSR can require a large amount of DRAM bandwidth and power. It will be appreciated that, in the context of a wireless and battery-powered HMD, chip size as well as bandwidth and power requirements can be very important, which can add to the challenges and difficulties associated with rendering mixed-reality scenes to a user.
As suggested above, many mixed-reality computer systems are untethered battery-powered devices that suffer operational power constraints. These constraints are designed to prolong the battery's lifespan so that the user can enjoy more time with the scene. However, many operations of the computer system significantly impact the computer system's battery lifespan. For example, performing data acquisition operations and LSR actions are prime examples of such battery-tolling operations. Accordingly, there exists a strong need in the field to efficiently improve the power consumption of systems that perform these types of operations.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is provided to illustrate only one exemplary technology area where some embodiments described herein may be practiced.